This invention relates to the removal of moisture and dust particles from air and, more particularly, to an apparatus which can be mounted on an underground coal mining machine for removing coal dust from the surrounding environment during mining operations.
This invention relates generally to the subject matter of co-pending U.S. patent applications, Ser. No. 950,548 filed Oct. 12, 1978, and Ser. No. 950,549 filed Oct. 12, 1978 (both of which are owned by the same entity which owns the instant invention), and represents an improvement over those inventions. This invention is also related to the subject matter of two U.S. patent applications filed on the same day herewith and owned by the same entity which owns the instant application, Ser. Nos. 037,962 and 037,963, filed May 10, 1979, and entitled, "Aerodynamic Sump Divider for Demister Unit" and "Sump Divider for Demister Unit", respectively. The subject matter of all of these applications is incorporated herein by reference for additional background information.
In underground coal mines, for example, continuous mining machines are used which generate large quantities of fine coal dust which must be removed from the air to reduce respirable dust levels to government specified limits. Relatively low dust levels are also critical for minimizing the possibility of a coal mine explosion.
The subject matter of the applications identified above represent significant advances in the art. By way of background, in air cleaning systems of this type moisture is introduced into flowing dirty air for encapsulating dirt particles. The flow path includes a demister unit which forces the air to change direction, causing the moisture and dust particles to be deflected from their normal flow path. This helps the moisture and dirt particles more easily to gravitate to a sump where they are removed from the flowing air stream.
In the two earlier-filed applications identified above, the sump is formed in part by a lower duct surface where the dirt-laden moisture collects and is removed. The sump portion can be formed several ways. In one, a slurry accumulating section is provided adjacent the rearward end of the lower collecting surface with a forwardly facing entrance for admitting moisture droplets and dust particles. Another is used in conjunction with a plurality of air guiding louvers, where an accumulating section located at the rear end of the collecting surface extends above the lower ends of the louvers. In yet another, gas inlet and outlet openings to the demister section have lower levels, the distance from the lower level of the inlet opening to the collecting surface being less than a comparable distance for the outlet opening.
Although these and the other designs disclosed in those two earlier-filed applications provide significant advantages over the prior art such as, for example, enabling a demister to be fabricated with a lower height, increasing operational efficiency, allowing noisy fans to be further removed from the operator, and providing a unit which can be retrofitted on existing mining machines, several drawbacks still exist.
For example, when the apparatus is mounted on a cutter arm of a continuous mining machine and subjected to continual up and down movement, liquid on the collecting surface tends to splash about and becomes re-entrained in the flowing air stream. The liquid also tends to surge from front to back and vice-versa which impedes even and continuous removal from the collecting surface.
Further, when a sump portion is formed with a liquid accumulation barrier adjacent the rear end of the lower collection surface and an entrance facing upstream is formed by using a plate which is connected at the top edge of the barrier and projects in the upstream direction, turbulence caused by air flowing over the plate contributes to liquid in the sump becoming re-entrained in the gas stream and significantly affects operational efficiency by impeding smooth air flow.